Lindsay Lohan has finally come clean on rumors about her incredibly shrinking body, admitting in the new issue of Vanity Fair that her low body weight was due to bulimia. She also tells the magazine that she has experimented with drugs in the past.

"I was sick," the singer/actress says in the magazine's February issue. "Everyone was scared. And I was scared too. I had people sit me down and say, 'You're going to die if you don't take care of yourself.' "

One of those interventions took place in May 2005 when Lohan — who was hospitalized Monday after an asthma attack (see "Lindsay Lohan Hospitalized After Asthma Attack") — hosted "Saturday Night Live." Castmembers Amy Poehler and Tina Fey, who had worked with Lohan in "Mean Girls," were concerned that the actress was getting too thin. "Amy was good and tough on her," Fey tells Vanity Fair, "saying, 'You're too skinny ... I'm not going to ask you why, but you're too skinny and I don't like it.' "

Fey and show producer Lorne Michaels also held an intervention of sorts, according to the magazine. They let Lohan know what they had witnessed with John Belushi and Chris Farley, who both died of drug overdoses, telling her they were concerned about her following the same self-destructive path.

"They sat me down," Lohan says, "literally before I was going to do the show, and they said, 'You need to take care of yourself. We care about you too much, and we've seen too many people do this,' and I just started bawling. I knew I had a problem and I couldn't admit it."

Even more convincing, Lohan says, was seeing images of her "SNL" appearance in Star magazine. "My arms were disgusting," she says. "I had no arms. My sister, she was scared. My brother called me, crying."

Just six months before the "SNL" appearance, Lohan had what she said should have been a wake-up call (see "Lindsay Lohan Hospitalized, Undergoing Tests"). "I started to get really bad head pains, I was shaking in my trailer," she recalls. "I got a fever of 102 and they were like, 'You need to go to the hospital.' I was like, 'No, I'm not going to the hospital.' I went back to my boyfriend's house, lay down on the bed. I started getting these shooting head pains, where I would wake up in the middle of the night. I kid you not, I was lying in that bed and I never heard someone scream so loud. I was screaming, throwing things, because the pains were so intense in my head, like someone was stabbing me in my head."

When Lohan finally sought medical attention and discovered she had a kidney infection, she considered it a cry for help. "I didn't want to complain, but that was my way to complain," she says, "to actually let everyone know, 'Yeah, I actually am really sick.' " She lost 15 pounds while in the hospital. "I wasn't eating. I was on an IV."

Lohan has since regained some of the weight, which she shows off by posing nude in the Vanity Fair photo spread. But according to the story, she displayed an appetite that suggests her binging-and-purging days may not be that far behind — such as ordering five pieces of chocolate cake to eat in private or placing several orders of curried chicken "because you never know who's going to drop by." But Lohan wasn't interested in hearing any more concern. "Don't ever say this to me, 'Are you OK?' " she says. "It's like, 'Yeah, motherf-----, I'm fine.' "

She also tells the magazine that she has experimented with drugs "a little," but then qualifies her remark. According to the article, "When asked later if those drugs included cocaine, [Lohan] gets flustered, denies it, and says, 'I don't want people to think that I've done ... you know what I mean? It's a sore subject. I've lost a family member over it, practically.' "

Still, Lohan says she's been through the worst and now considers herself in a position to help others.

"You have to learn for yourself and you have to hit rock bottom sometimes to get yourself back up to the top," Lohan says. "Going through sh-- makes me that much stronger. [And] I'm in a place where I can really make an impact on people and really help ... people with anorexia. I can change that a little bit. I'm not encouraging going out and getting a fake ID and going off the deep end and having an eating disorder. I'm saying, if you at least admit those kinds of things, that that might happen, then they don't feel the urge to go out and do that."